SAW tapped delay lines for new potential circuit applications

Abstract

Two applications for SAW tapped delay lines are discussed. The first uses a SAW differential tapped delay line (TDL) to detect an important property of a single BPSK-type signal, namely, its chirp rate. For this application, differential delay lines are required, since it would be too difficult to build standard delay lines having delay times of the order of 50 ns due to their feedthrough and triple-transit problems. After the BPSK signal is fed into the TDL, the output of the TDL is fed into either a summer or mixer device whose output can then be viewed on an oscilloscope. Both summer and mixer circuits using the SAW differential TDL are analyzed, and results are shown for the summer circuit along with the impulse response for the tapped differential delay line by itself. The second application uses a TDL in an amplifier feedback loop circuit to replace the inverse transform of a chirped Fourier transform (CFT) processor for CW input signals. Some of the limitations of the TDL method are discussed. A staggered channelized method is presented for the SAW TDL that eases fabrication and minimizes reflections utilizing a minimum number of output taps. >